Receptor antagonists are chemical compounds that act as cellular receptor ligands that do not provoke a biological response upon binding to a receptor, but block or dampen agonist-mediated responses. In pharmacology, antagonists have affinity but no efficacy for their cognate receptors, and binding thereto will disrupt the interaction and inhibit the function of an agonist or inverse agonist at the receptor site. Antagonists mediate their effects by binding to the active site or to allosteric sites on receptors, or they may interact at unique binding sites not normally involved in the biological regulation of the cellular receptor's activity. Antagonist activity may be reversible or irreversible depending on the longevity of the antagonist-receptor complex, which, in turn, depends on the nature of antagonist receptor binding. The majority of drug antagonists achieve their potency by competing with endogenous ligands or substrates at structurally-defined binding sites on receptors. Angiogenesis is directly involved in a number of pathological conditions such as tumor growth, inflammation and diabetic retinopathy. Current approaches to the treatment of abnormal angiogenesis in the eye include laser therapy, which destroys some retinal tissue in order to preserve some vision, and the administration of anti-VEGF antibody and/or anti-VEGF RNA aptomer. There remains a clear need for improved methods and agents for prevention and treatment of conditions involving abnormal angiogenesis and harmful pathological angiogenesis in the tissues of the eye
Sphingosine 1-phosphate (S1P) is a lipid mediator that regulates various biological processes, such as cell proliferation, migration, survival and differentiation. S1P which is generated by the phosphorylation of sphingosine by sphingosine kinase 1 (Sphk1) and sphingosine kinase 2 (Sphk2), is degraded by S1P-specific phosphatases and a lyase. It is a ligand with high affinity for five (5) G-protein coupled S1P receptors on the cell-surface, S1P1R, S1P2R, S1P2R, S1P4R and S1P5R, that regulate distinct intracellular signaling pathways. S1P1, S1P2 and S1P3 receptors are widely expressed, whereas S1P4 and S1P5 expression is prominent in cells of the immune and nervous systems, respectively. The S1P1 receptor couples exclusively to Gi signaling pathway, whereas S1P2 and S1P3 receptors couple to Gi as well as to the Gq and G12/13 pathways. However, S1P2 activates G12/13 potently, whereas S1P3 activates Gq preferentially.
FTY720 is a potent immuno-modulator that has a mechanism of action which includes phosphorylation into FTY720-P, which is an agonist for four of the five S1P receptors in T lymphocytes. It was shown previously that FTY720 is a potent modulator of lymphocyte trafficking, however, the effect of FTY720 on vascular elements was previously unknown.
It has been demonstrated that vascular endothelial cells contain enzyme systems that “activate” FTY720 and its analogs. Cultured endothelial cells such as human umbilical vein endothelial cells (HUVEC) are accepted in in vitro model systems for studying angiogenesis. Upon incubation with HUVEC conditioned medium or cell extracts, FTY720 is phosphorylated and is able to activate the endothelial cells to migrate in a pertussis-toxin sensitive manner, suggesting that it is activating the Gi-coupled S1P receptors. It is shown herein that endothelial cell-derived sphingosine kinase-2 (SK2) is involved in the activation of FTY720 into FTY720-P.
S1P receptors also regulate important physiological functions of the vascular system, such as vascular morphogenesis and maturation, cardiac function, vascular permeability and tumor angiogenesis. Indeed, S1P1 null embryos die due to massive hemorrhage at E 12.5-14.5 days of gestation since the S1P1 receptor is essential for proper stabilization of the embryonic vascular system by promoting the formation of strong N-cadherin-based junctions between endothelial and vascular smooth muscle cells. However, mice that lack either the S1P2 or the S1P3 receptor are viable and fertile.
Interestingly, S1P1/S1P2 double null embryos showed a more severe phenotype than S1P1 single null embryos, suggesting that S1P2 receptor is also significant during embryonic vascular development. In addition, S1P2 null mice are profoundly deaf due to vascular abnormalities in the stria vascularis of the inner ear and degeneration of sensory hair cells of the organ of Corti. Moreover, a mutation in the zebrafish gene miles-apart (Mil), an S1P2 analog, results in cardiac developmental defects (cardia bifida) due to the defective migration of cardiomyocyte precursors, underscoring the significance of this receptor for the fish cardiac development. However, the role of the S1P2 receptor in vascular development and pathology is an active area of study.
The process of forming new blood vessels is termed angiogenesis. During angiogenesis, vascular endothelial cells undergo orderly proliferation, migration, and morphogenesis to form new capillary networks. Under normal or non-pathologic conditions, angiogenesis occurs under well-defined conditions such as in wound healing, tissue and cellular response to ischemia, and during embryonal and fetal development. However, persistent or uncontrolled angiogenesis can lead to a variety of disease states or conditions and, in the case of solid tumors, may be a necessary condition to maintain the disease state.
U.S. Pat. No. 7,838,562 to Hla et. al. discloses and claims a number of agonist compounds of vascular endothelial sphingosine-1-phosphate receptors that are asserted to be useful in the treatment of vascular permeability disorders, comprising the administration of a therapeutically effective amount of a compound selected from the group comprising 2-amino-2-[2-(4-octaphenyl)ethyl]propane-1,3 diol, or 2-amino-2-methyl-4-[4-heptoxy-phenyl]butane-1-ol. The vascular permeability disorder may be any one associated with endothelial injury, thrombocytopenia, ischemic peripheral vascular disease, any one of a number of peripheral vascular disorders associated with diabetes, Dengue hemorrhagic fever, acute respiratory distress syndrome, vascular leak syndrome, or a combination thereof. The afore-mentioned compounds can be phosphorylated by sphingosine kinase-2 into the phosphorylated forms which serve as sphingosine-1-phosphate receptor agonists.
U.S. Pat. No. 7,910,626 to Brinkman et. al. discloses compounds for treating chronic or congestive heart failure comprising administering to said subject a therapeutically effective amount of 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol in free form or a pharmaceutically acceptable salt or phosphate thereof.
U.S. Pat. No. 8,114,902 to Kiuchi et. al. discloses and claims compounds useful in the treatment or prophylaxis of auto-immune diseases or acute and chronic rejection due to organ or tissue transplantation, graft vs host (GvH) disease due to bone marrow transplantation and the treatment or prophylaxis of allergic diseases. Particularly suitable compounds include the pharmaceutically acceptable acid addition salt, hydrate or a solvate of 2-amino-2-{2-[2′-fluoro-4′-(4-methylphenylthio)biphenyl-4-yl]ethyl}propane-1,3-diol and 2-amino-4-[2′-fluoro-4′-(4-methylphenylthio)biphenyl-4-yl]-2-(phosphoryloxymethyl) butanol.
U.S. Patent Appln. No. 2011/0015159 also to Hla et. al. discloses and claims a number of novel agonists of vascular endothelial sphingosine-1-phosphate receptors. Known compounds agonists such as FTY720 can be phosphorylated by sphingosine kinase-2 into the phosphorylated forms which serve as sphingosine-1-phosphate receptor agonists. These vascular endothelial receptor agonists can be formulated into pharmaceutical compositions for treating vascular permeability disorders and unwanted vascular endothelial cell apoptosis.
WO 01/98301 to Kawasaki et. al. relates to new pyrazolopyridine compounds having sphingosine-1-phosphate receptor antagonistic activity and their use in pharmaceutical compositions as fibrosis remedies that contain Sph-1-P receptor antagonistic activity or pharmaceutically acceptable salts as an active ingredient. Specifically, the invention relates to new compounds of the formula:
where in R1, R2 and R3 are each C1-8 alkyl and the like; R4 is hydrogen and the like; R5 and R6 are each independently hydrogen, C1-8 alkyl, C1-6 alkoxy, halogen; X is NH—, —O—, —CH2—, Y is NH—; Z is CO—; W is NH—; and A is aryl or heteroaryl, These compounds are asserted to have that have therapeutic efficacy for liver, kidney, and lung fibrosis or arteriosclerosis caused by thickening of vascular smooth muscle.
European patent application EP 1 424 078 A1 to S. Nakade et. Al discloses and claims a number of S1P antagonists as remedies for respiratory diseases comprising shingosine-1-phosphate receptor controller. These compounds can be used to treat or prevent airway constriction, bronchial asthma and chronic obstructive pulmonary disease (COPD), pulmonary emphysema, tracheostenosis, diffused panbronchialitis, or bronchitis with infection, connective-tissues diseases or transplantation, lymphangioleiomyomatosis, adult respiratory distress syndrome (ARDS), interstitial pneumonia, lung cancer, hypersensitive pneumonitis or idiopathic interstitial pneumonia.
WO 2011/048287 A1 to W. K. Fang et. al discloses and claims condensed ring pyridine compounds as subtype-selective modulators of sphingosine-1-phosphate-2 (S1P2) receptors. These compounds can be used to treat or prevent diseases and conditions consisting of ocular diseases: cardiac diseases or conditions, fibrosis, pain and wounds.
U.S. Patent Appln. No. 2009/00004207 to Hla et. al. discloses and claims a number of novel agonists of vascular endothelial sphingosine-1-phosphate receptors. Known compounds agonists such as FTY720 can be phosphorylated by sphingosine kinase-2 into the phosphorylated forms which serve as sphingosine-1-phosphate receptor agonists. These vascular endothelial receptor agonists can be formulated into pharmaceutical compositions for treating vascular permeability disorders and unwanted vascular endothelial cells. Known agonists such as FTY720 can be phosphorylated by sphingosine kinase-2 into the phosphorylated forms which serve as sphingosine-1-phosphate receptor agonists. These vascular endothelial receptor agonists can be formulated into pharmaceutical compositions for treating vascular permeability disorders and unwanted vascular endothelial cell tumors.
U.S. Patent Appln. No. 2011/041287 also to Hla et al discloses a number of compounds that inhibit abnormal angiogenesis in the eye, particularly in the retina. The compounds are asserted to be effective inhibitors of the receptor activity of the S1P2 receptor. The compositions include the S1P2 receptor antagonist and an opthalmically acceptable excipient.
In order to determine the role of the S1P2 receptor in mammalian vascular development, the retinal vascular development of mice lacking the S1P2 receptor was examined under physiological (normal retina development) and patho-physiological conditions (ischemic-driven retinopathy). Post-natal vascular development of the mouse retina provides an attractive model system to explore the mechanisms of angiogenesis and vascular stabilization. After birth, endothelial cells emerge from the optic disc and form the primary vasculature of the mouse retina. Vessels that grow with radial orientation are formed along the retina neuronal and astrocytic plexus. On the other hand, pathological retina angiogenesis produces abnormally growing and chaotically oriented dysfunctional vessels that grow into the vitreous fluid as “vascular tufts” and eventually lead to vision loss. This phenotype is common in the pediatric retinopathy of prematurity (ROP) and in diabetic retinopathy of the adult.
It has been shown that the angiogenic process proceeds normally in S1P−/−2 mice during normal retinal development. However, when mice were exposed to ischemic stress, S1P2−/− retinas appear to have increased “physiological” intra-retinal angiogenesis and reduced “pathological” intra-vitreal neo-vascularization. It was further demonstrated that the S1P2 receptor is required for inflammatory cell infiltration, induction of the pro-inflammatory and pro-angiogenic enzyme cyclo-oxygenase (COX)-2 and the suppression of the endothelial nitric oxide synthase (eNOS) which produces the vasodilator nitrous oxide (NO). This study identified S1P signaling by the S1P2 receptor as a novel target for the prevention and/or treatment of vision-threatening retinopathies.
In a paper by Schwalm Pfeilschifter and Huwiler (Biochimica et Biophysica Acta 1831 (2013) 239-250) the general effects of extracellular and intracellular S1P on the multi-step cascade of pathological fibrogenesis including tissue injury, inflammation and the action of pro-fibrotic cytokines that stimulate ECM production and deposition is examined, The current knowledge about the involvement of S1P is suggested as being involved in the control of signaling in the development of organ fibrosis of the lung, kidney, liver, heart and skin. It is further shown that targeting the sphingosine kinase-1/S1P signaling pathway offers therapeutic potential in the treatment of various fibrotic processes.
In one embodiment of the present invention, a method of treating abnormal angiogenesis in the eye comprises administering to an individual in need thereof an effective amount of an S1P2 receptor antagonist. As used herein, the term “treating” includes the administration to an individual suffering from abnormal angiogenesis of the eye as well as the administration, both preventatively or prophylactically to an individual at risk of abnormal angiogenesis of the eye. Administration of an S1P2 receptor antagonist to an individual at risk for abnormal angiogenesis of the eye can prevent abnormal angiogenesis of the eye. In one embodiment, the individual is at risk of, or has been diagnosed with, abnormal angiogenesis of the eye.
In another embodiment of the invention, the method of treatment involves the pathological angiogenesis in the eye associated with an ocular neo-vascular disease. This type of disease is characterized by invasion of new blood vessels into the structures of the eye such as the retina or cornea. It is the most common cause of blindness and is involved in approximately twenty (20) eye diseases. In age-related macular degeneration, the associated visual problems are caused by an in-growth of choroidal capillaries through defects in Bruch's membrane with proliferation of fibro-vascular tissue beneath the retinal pigment epithelium. Angiogenic damage is also associated with diabetic retinopathy, retinopathy of prematurity, corneal graft rejection, neovascular glaucoma, and retro-lental fibroplasia. Other diseases associated with corneal neo-vascularization include, but are not limited to, epidemic kerato-conjunctivitis, Vitamin A deficiency, contact lens over-wear, atopic keratitis, superior limbic keratitis, pterygium keratitis sicca, sjogrens disease, acne rosacea, phylectenulosis, syphilis, Mycobacteria infections, lipid degeneration, chemical burns, bacterial ulcers, fungal ulcers, Herpes simplex infection, Herpes zoster infections, protozoan infections, Kaposi's sarcoma, Mooren's ulcer, Terrien's marginal degeneration, marginal keratolysis, rheumatoid arthritis, systemic lupus, polyarteritis, trauma, Wegener's sarcoidosis, scleritis, Stevens-Johnson's disease, pemphigoid, and radial keratotomy.
Other diseases associated with retinal/choroidal neo-vascularization include, but are not limited to, diabetic retinopathy, macular degeneration, sickle cell anemia, sarcoidosis, syphilis, pseudoxanthoma elasticum, Paget's disease, vein occlusion, artery occlusion, carotid obstructive disease, chronic uveitis/vitritis, Mycobacterial infections, lyme disease, systemic lupus erythematosis, infant retinopathy, Eales' disease, Behcet's disease, retinitis or choroiditis caused by bacterial or viral infection, presumed ocular histoplasmosis, Best's disease, myopia, optic pits, Stargardt's disease, pars planatitis, chronic retinal detachment, hyper-viscosity syndromes, toxoplasmosis, trauma and post-laser complications. Other eye-related diseases include, but are not limited to, diseases associated with rubeosis (neo-vascularization of the eye) and diseases caused by the abnormal proliferation of fibrovascular or fibrous tissue, including all forms of prolific vitreo-retinopathy.
In another embodiment, pathological angio-genesis of the eye is associated with a neoplastic eye disease. Neoplastic eye diseases include primary ocular tumors, such as uveal melanomas, melanocytomas, retinocytomas, retinal hematomas and choristomas, retinal angiomas, retinal gliomas and astocytomas, choroidal hemangiomas, choroidal neurofibromas, choroidal hematomas and choristomas, ocular lymphomas and ocular phakomatoses; and metastatic ocular tumors related to choroidal and retinal neo-vascularization. Similar to the non-neoplastic diseases, the above tumors also share the retinal neovascularization as a key component.
Pathological angiogenesis and several types of inflammatory disease have been correlated with increased S1P2 receptor levels. JTE013 is the only currently available S1P2 receptor selective antagonist compound. However, the anecdotal reports have confirmed that JTE013 has very poor in vivo characteristics, based at least in part on its rapid metabolic clearance. These characteristics limit the efficacy and usefulness of JTE013 in treating and preventing sphingosine-1-phosphate-mediated diseases and disorders.
Ferrer and Hla have reported that neuroblastoma cell lines over-express S1P2 receptors, and suggest that S1P2 antagonists could be used for this pediatric cancer. Van Brocklyn and Young, and others have shown the importance of S1P2 receptors in the morphology of cellular invasiveness and its' proliferation in glioma cells (which are responsible for glioblastoma multiforme).
JTE013 is a well known sphingosine 1-phosphate receptor 2 (S1P2) class of antagonists that have the potential to be useful as anti-angiogenesis agents in cancer, atherosclerosis, and other inflammatory diseases. The present invention comprises the development of a group of sphingosine 1-phosphate receptor 2 (S1P2) receptor derivatives that function as S1P2 antagonists that are useful as anti-angiogenesis agents in cancer, atherosclerosis, and in other inflammatory disorders by blocking or inhibiting the signaling of the sphingosine 1-phosphate 2 receptor (S1P2).